afaik, throttling is featured in all modern cpus -- for many years now. It came more or less in conjunction with heatspreaders. One obvious & simple way to detect is with an AC power meter -- total power draw starts yoyoing down & up as throttling begins when a steady state stress utility like prime95 is used.

I don't think that's quite right. CnQ applies only in low power states, to reduce power in idle, much like Inte's Speedstep. This was adopted from Notebooks. Not sure if AMD (or Intel, for that matter) actually named the throttling-at-max-power utility.

Post subject: Re: How to detect/observe CPU power (thermal) throttling?

Posted: Mon Aug 20, 2012 12:24 pm

Patron of SPCR

Joined: Wed Dec 15, 2004 12:00 pmPosts: 3307Location: Essex, England

Quote:

Not sure if AMD (or Intel, for that matter) actually named the throttling-at-max-power utility.

This thread has put doubt into my mind, I have never seen a CPU throttle for certain, i.e. I didnt have CPU-Z installed and watched the clock speeds whilst it was overheating, but I was quite certain that this feature was introduced first with the P4, and then the Athlon, and I would assume every CPU since.

Many BIOS's have a "CPU throttling option" with they typical options of 60C, 65C and 70C, I have always set it at 60C when given the choice - But I have never actually put this to the test, although I have known some laptops to slow down when their heat-sinks are clogged with dust, fluff and hair, but I still don't have any personal evidence......

The short version if you don't want to be bored by Intel documents, there are two basic ways CPU overheating is controlled, one is PROCHOT (short for processor hot)basically a single bit flag on each CPU die that gets tripped when the TCC (Thermal Control Circuit) limit (set by INTEL) is reached this pretty much just tells the board to cut power to the CPU.

The other methods and probably more relevant to the OP's question about lowering the frequency of the CPU are called TM and TM2, (Thermal Monitor,Thermal Monitor2)Basicly TM changes the duty cycle of the internal processor clocksAnd TM2 causes the processor to adjust its operating frequency (by dropping the bus-to-core multiplier to its minimum available value) and input voltage identification (VID) value. This combination of reduced frequency and VID results in a reduction in processor power consumption.

Post subject: Re: How to detect/observe CPU power (thermal) throttling?

Posted: Mon Aug 20, 2012 2:30 pm

Patron of SPCR

Joined: Wed Dec 15, 2004 12:00 pmPosts: 3307Location: Essex, England

Quote:

The short version if you don't want to be bored by Intel documents, there are two basic ways CPU overheating is controlled,one is PROCHOT (short for processor hot)basically a single bit flag on each CPU die that gets tripped when the TCC (Thermal Control Circuit) limit (set by INTEL) is reached this pretty much just tells the board to cut power to the CPU.

The other methods and probably more relevant to the OP's question about lowering the frequency of the CPU are called TM and TM2, (Thermal Monitor,Thermal Monitor2)Basicly TM changes the duty cycle of the internal processor clocksAnd TM2 causes the processor to adjust its operating frequency (by dropping the bus-to-core multiplier to its minimum available value) and input voltage identification (VID) value. This combination of reduced frequency and VID results in a reduction in processor power consumption.

Erm sorry for the longish post i got a bit carried away

Don't apologise for such a short and very, very sweet post.

The TM/TM2 rings some bells from the distant past, and I would love to have a system to torture to see it in action for myself, just because

From what i can remember most software takes best guess approaches to measuring the true temperature of modern day CPU's speaking about Intel, And i dare say it's the same for AMD, a quote from the documents of Realtemp.

Intel designed these temperature sensors to control thermal throttling and thermal shut down and for those purposes, they tend to work excellent. They were never designed to be used to report accurate core temperatures.

So it's hard to know for sure when the TJmax(Intel) or TCase Max(AMD) is reached as TJMax (IDK about AMD) is not a clearly defined value.

If you wanted to know a best guess for when the CPU is throttling due to overheating you would be looking for the TJMax or TCase Max for that particular CPU, AFAIK Core Temp like all other software uses a best approximation approach.

You would then have to use something like core temp to get a rough idea of what the CPU's TJMax or TCase Max is, As well as using something like CPU-Z at the same time to view the clock multiplier, core voltage, and Frequency of the CPU.Watch for these to drop when you get close (could be +-10c) to TJMax, TCase Max.

All the while running your favorite stress test, Personally i used IntelBurnTest works on AMD to.But if i'm honest i would be very worried if any CPU reached 117° C like the OP said IDK if AMD run hot normally but there comes a point when reducing the noise a PC makes can be taken to far if your going to cook you components due to lack of good air flow.

As for the other end of the scale like MikeC said AMD used to use C'n'Q I think they now call it P-States and for Intel its C-States, but that's a hole other kettle of fish.

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